1. Field of the Invention
This invention relates to an improvement in a fluid coking process. More particularly, this invention relates to a fluid coking process conducted in the presence of an alkaline earth metal ferrite-containing catalyst.
2. Description of the Prior Art
Fluid coking is a well-known process which may be carried out with or without recycle of the heavier portion of the fluid coking zone effluent. As is well known in the art, the fluid coking process, as shown for example, in U.S. Pat. No. 2,881,130, which is hereby incorporated by reference, uses a fluid coking vessel and an external heating vessel. A fluid bed of solids, preferably coke particles produced by the process having a size in the range from about 40 to about 1000 microns is maintained in the coking zone by upward passage of fluidizing gas, usually steam, injected at a superficial velocity usually between 0.3 and 5 feet per second. The temperature in the fluid coking bed is maintained in the range of about 850.degree. to about 1400.degree. F., preferably between 900.degree. and 1200.degree. F. by circulating solids (coke) to the heating vessel and back. The heavy oil to be converted is injected into the fluid bed and upon contact with the hot solids undergoes pyrolysis evolving lighter hydrocarbon products in vapor phase, including normally liquid hydrocarbons, and depositing a carbonaceous residue (coke) on the solids. The turbulence of the fluid bed normally results in substantially isothermal reaction conditions and thorough and rapid distribution of the heavy injected oil. The feed rate and temperature are controlled to maintain the bed in a fluidized state. Product vapors, after removal of entrained solids, are withdrawn overhead from the coking zone and sent to a scrubber and fractionator for cooling and separation. The end boiling point of distillate fractions obtained from the process is usually about 1050.degree. F. to about 1200.degree. F. and the remaining heavy ends are usually recycled to extinction.
U.S. Pat. No. 4,269,696 discloses an integrated fluid coking and gasification process in which a solid cracking catalyst is added to the coker chargestock.
U.S. Pat. No. 3,707,462 discloses a fluid coking process in which calcium oxide or a precursor thereof is present in the fluidized bed coking zone.
U.S. Pat. No. 4,229,283 discloses fluid hydrocoking with the addition of dispersible metal compounds in the coker feed. Metallic ashes recovered from the gasification of the coke are recycled to the coker feed.
It has now been found that the presence of an alkaline earth metal ferrite-containing catalyst in the fluid coking zone will permit conducting the fluid coking reaction at a lower temperature at a constant feed rate or will permit an increase in feed rate at a constant temperature.